View full sizeThe Associated PressPresident Barack Obama on the South Lawn of the White House.

A white separatist pleaded guilty in a Portland courtroom Tuesday to writing a letter last year from the Oregon State Penitentiary in which he threatened to kill President Barack Obama.

U.S. District Judge Anna J. Brown found David Earl Anderson, 27, guilty of threatening to kill the president, a charge that carries a maximum penalty of five years in prison.

Federal prosecutor Stephen Peifer told the court that Anderson had written several letters from prison in which he threatened Obama's life, including one to Oregon State Police.

Anderson admitted to Brown that on Oct. 26, 2009, he mailed a letter to a family in Utah in which he threatened the life of the president.

"I am 100 percent down with my own white race," he wrote, explaining later in the letter, "Our race needs to stay strong."

Multnomah County JailDavid Earl Anderson

Anderson's letters spelled out a group plot to kill the president.

"The Secret Service investigated and determined that the group referenced by Anderson did not exist," Peifer told The Oregonian.

The prosecutor said in court that the government intends to ask for Anderson to be imprisoned for up to four years. Anderson's lawyer, C. Renee Manes, said she plans to ask for a sentence of about a year to run concurrently with the prison time he already is serving.

Anderson was sent to prison in August 2007 for identity theft, supplying contraband, using a minor in a drug offense and escape, records show. He was expected to get out of prison, at the earliest, in November 2012. But he was charged with new crimes last year.

Authorities say he escaped a secure unit at Salem's Oregon State Hospital in August 2009 with the help of a girlfriend. Anderson was arrested a day later in Utah.

He shared his reasons for escaping in letters to Salem's Statesman Journal, which carried a story about the escape last November.

"How I escaped was I had a pair of bolt cutters sent into me concealed in a DVD player that was gutted out and put back in the packing like it was brand new," Anderson wrote the newspaper. He complained that he had received "little to no help" for treatment of his mental illness.

Anderson had served an earlier stretch of five years at the state hospital for what Manes described in court papers as "significant mental health issues." He is now being held at the federal prison in Sheridan, where he has been put on psychotropic medications, she said.